Industrial solvents containing one or more chlorine atoms, including trichloroethene (TCE), tetrachloroethene (PCE), 1,1,1-trichloroethane (TCA), and the dechlorination daughter products cis-1,2-DCE and vinyl chloride. The dominant DNAPL source-zone contaminant class at industrial sites worldwide.
Chlorinated solvents were used for metal degreasing, dry cleaning, semiconductor manufacturing, and aerospace cleaning from the 1940s onward, with peak production in the 1970s. Spills and waste-handling releases at thousands of industrial and military sites created the dominant DNAPL source-zone problem in groundwater remediation today.
The parent compounds (PCE, TCE, 1,1,1-TCA) undergo sequential dechlorination under anaerobic conditions to less-chlorinated daughters. Incomplete dechlorination accumulates cis-1,2-DCE and vinyl chloride; the latter is a Class 1 human carcinogen with a U.S. EPA drinking water MCL of 2 micrograms per litre, and its accumulation is a defining concern for natural attenuation and ERD remedies. Complete dechlorination to ethene requires Dehalococcoides species, often supplied by bioaugmentation.
Also known as: chlorinated solvents, chlorinated ethenes, TCE, PCE, vinyl chloride, DCE, 1,1,1-TCA.
Chlorinated Solvents (TCE, PCE, TCA, DCE, VC): treatment approach
Man-made chlorinated aliphatic hydrocarbons — tetrachloroethylene (PCE), trichloroethylene (TCE), 1,1,1-trichloroethane (TCA), cis-1,2-DCE, and vinyl chloride — that formed the industrial degreasing and dry-cleaning solvent market for four decades and left the densest DNAPL groundwater plumes in North America.
Per- and polyfluoroalkyl substances: a class of more than 12,000 synthetic compounds built around exceptionally stable carbon-fluorine bonds. PFAS is the family name, not a single chemical. PFOA and PFOS are two specific members of this class.
Perfluorooctanoic acid: a specific eight-carbon long-chain PFAS compound, historically used in non-stick coatings and AFFF firefighting foam. Classified by IARC in 2023 as Group 1, carcinogenic to humans.
Perfluorooctane sulfonic acid: a specific eight-carbon long-chain PFAS compound, historically the active surfactant in 3M Scotchgard and AFFF firefighting foam. Classified by IARC in 2023 as Group 2B, possibly carcinogenic to humans.
Polychlorinated dibenzo-p-dioxins and related furans: highly persistent, fat-soluble chlorinated compounds formed as unintended byproducts of combustion, chlorine-based manufacturing, and herbicide production, with TCDD among the most toxic substances ever characterized.